Powerfully-built Ridley, who stood over 6ft tall, admitted manslaughter and unlawful wounding. After he was arrested, police found testosterone used by body builders at his home. The defendant, of Sceptre Place, Newcastle, was told he could be freed after serving just half his sentence.

The couple were enjoying a rare night off together after Corporal Chacksfield had returned the previous month from Camp Bastion in Afghanistan. Sergeant Chacksfield was on exercise in the North East and was allowed a night off to spend time with his wife.

A number of witnesses saw Ridley's unprovoked attack in Newgate Street, with some saying one punch knocked out the couple, others saying two. All agreed the punch was thrown without warning and for no reason. Judge Faulks said Ridley had bumped into the 31-year-old soldier before striking out.

Outside court, his 32-year-old widow, originally from Derby, said: "I am obviously disappointed in the sentence, on the other hand they caught somebody and he is behind bars. Although it doesn't seem fair, I believe he will get his comeuppance in the end. What goes around, comes around."

Sgt Chacksfield, originally from Tamworth, Staffordshire, and serving with the 14th Signal Regiment (Electronic Warfare), based in Pembrokeshire, was a 6ft 2in, 14 stone "gentle giant", she said.

"He loved life and was just a placid gentleman. He didn't have any enemies. You could almost understand it if he had died on active service, but not on a night out. I know Chris wouldn't want me to sit around and mope - I have (daughter) Sofia to think about. We have to move forward," she added.